text: Solder fittings are smooth, and easily slip onto the end of a tubing section. Both the male and female ends of the pipe or pipe connectors are cleaned thoroughly then coated with flux to make sure there is no surface oxide and to ensure that the solder will bond properly with the base metal.  The joint is then heated using a torch, and solder is melted into the connection. When the solder cools, it forms a very strong bond which can last for decades. Solder-connected rigid copper is the most popular choice for water supply lines in modern buildings. In situations where many connections must be made at once (such as plumbing of a new building), solder offers much quicker and much less expensive joinery than compression or flare fittings.  The term sweating is sometimes used to describe the process of soldering pipes.